This invention relates to an arc-resistant deflection yoke and the fabrication thereof and more particularly to toroid-wound deflection yokes suitable for use in the cathode ray tube deflection system of a television receiver wherein the yoke is resistant to transmission of arcs which may occur in the cathode ray tube.
One of the problems associated with cathode ray tubes, and especially cathode ray tubes employed in present-day television receivers wherein ever higher high voltage potentials are being utilized, is internal arcing. It has been found that internal arcs in cathode ray tubes are often of a magnitude of several hundred AMPS. However, such arcs usually are of very short duration such as about 0.1 micro-seconds for example.
Also, it has been found that internal arcing in a cathode ray tube causes a relatively large pulse current flow in the internal aquadag coating deposited on the inner surface of the funnel portion of the cathode ray tube. In other words, the aquadag coating on the funnel portion of the cathode ray tube is surrounded by a deflection yoke externally associated with the cathode ray tube. Thus, the aquadag coating or the arc path behaves as a large single turn primary winding having a large pulse current flow which passes through the center of the associated deflection yoke. As a result, a relatively large pulse potential tends to be induced into the windings of the deflection yoke and, in turn, undesirably applied to circuitry associated with the windings. As a result, component burn out problems are frequently encountered.
As set forth in the prior art, specifically U.S. Pat. No. 3,631,902 issued on Jan. 4, 1972 and assigned to the Assignee of the present application, a minimum of electrostatic and magnetic cross-induction is achieved with a deflection yoke wherein the horizontal and vertical deflection windings are in a mirror image relationship. In such a configuration, an introduced pulse potential is quickly transmitted through the windings since there is a minimum of inductive and capacitive losses. In other words, the mirror-image windings act as a very efficient transformer for quickly conveying an applied energy pulse therethrough.
Although the above-described deflection yokes having mirror-image windings have been and still are used in many cathode ray tube deflection systems with excellent results, it has been found that there are occasions and apparatus which does not lend itself to such a deflection yoke configuration. For example, one known form of apparatus included a cathode ray tube experiencing internal arcing which appeared in the aquadag coating or arcing path as a very high pulse current having a very short duration. In turn, this very high and fast pulse current traveled rapidly through the mirror-image windings of the deflection yoke and arced to a high voltage source providing a path for high voltage through the deflection windings to circuitry associated therewith and resulted in component failure in the associated circuitry.